Pumping

ABSTRACT

A pump and a method of moving molten metal is provided in which a tube open at one end and closed at the other end cooperates with a secondary tube received within it, open at both ends, to pump metal from the open end of the tube down a space between the tube and secondary tube to the closed end of the tube and then return the metal up the centre of the secondary tube. A simpler way of providing circulation of molten metal is provided.

This invention concerns improvements in and relating to pumping,particularly of molten metal.

A variety of prior art systems for pumping or otherwise moving moltenmetal from one location to another exist. These systems are based arounda layout which includes a conduit leading into the pump from one side,the pumping location and a further conduit leading away from the pump onanother side. The conduit and further conduit are separate from oneanother and separately connected to the location or locations from whichthe pump receives the metal to be pumped and to which the pump pumps themetal.

Such systems take up significant space and require two sets ofappropriate connections and conduits.

The present invention has amongst its aims to provide an alternativemolten metal mover. The present invention has amongst its aims toprovide a pump for molten metal which requires less space to operateand/or requires less connections to operate.

According to a first aspect of the invention we provide a pump formolten metal, the pump comprising a tube, the tube being open at one endand closed at the other end, one or more side walls extending betweenthe open and closed ends, an electrical conductor being wrapped aroundthe tube, a secondary tube being provided within the tube, the secondarytube having a through aperture extending from a first end to a secondend and being spaced from at least a part of the side wall of the tubeand at least a part of the closed end of the tube.

The internal profile of the tube may be configured to promote flow intothe tube at the periphery of the tube and/or to promote flow out of thetube at the centre of the tube, preferably at the same time.

According to a second aspect of the invention we provide a pump formolten metal, the pump comprising a tube, the tube being open at one endand closed at the other end, one or more side walls extending betweenthe open and closed ends, an electrical conductor being wrapped aroundthe tube.

The internal profile of the tube may be configured to promote flow intothe tube at the periphery of the tube and/or to promote flow out of thetube at the centre of the tube, preferably at the same time.

Preferably a secondary tube is provided within the tube. The secondarytube may have a through aperture extending from a first end to a secondend. The secondary tube may be spaced from at least a part of the sidewall of the tube and at least a part of the closed end of the tube.

The first and/or second aspects may further include the followingfeatures, options or possibilities.

The tube may be of refractory, for instance silicon carbide. The tubemay extend along an axis. The tube may be of circular cross-section.Preferably the tube is of constant cross-section between the open endand the start of the closed end.

The open end of the tube may be of circular cross-section, preferablyperpendicular to its axis. The open end of the tube may be connected toa vessel, for instance a furnace, holding furnace or the like. Amounting element provided around at least a part of the open end may beused to mount the pump on the vessel. The open end of the tube may abuta part of the vessel, for instance a refractory lining. The open end ofthe tube may have a diameter of between 10 to 50 cm.

The closed end of the tube may be formed by a tapering of the side wallsand/or cross-sectional shape of the tube. The closed end may be formedof a series of circular cross-sections of decreasing diameter. Theclosed end of the tube may be dome shaped, particularly a dome in whichthe internal profile of the dome is exposed to the inside of the tube.The closed end of the tube may initially dome inwards, and preferablyhas a middle portion which extends back towards the open end of thetube. The middle portion may be dome shaped, particularly a dome inwhich the external profile of the dome is exposed to the outside of thetube.

Preferably the tube has a single side wall.

The electrical conductor is preferably wrapped around the tube in asingle coil. The electrical conductor may be spaced from the tube, forinstance by an insulator and/or magnetic field enhancing material. Theelectrical conductor may be clamped in position, preferably relative tothe tube. The clamping may be provided by a framework which encloses thetube and conductor. Locations for mounting the pump on a vessel may alsobe provided on the framework.

Preferably connections are provided for attaching the electricalconductor to a power supply.

The secondary tube may be of refractory material, for instance siliconcarbide. The secondary tube may extend along an axis, preferably thesame axis as the tube. The secondary tube may be of circularcross-section. Preferably the secondary tube is of constantcross-section between its open ends.

The first and/or second open ends of the secondary tube may be ofcircular cross-section, preferably perpendicular to its axis. The firstopen end of the tube may be in fluid connection with a vessel, forinstance a furnace, holding furnace or the like, and particularly thesame vessel as the tube is in fluid location with. Preferably both theopen end of the tube and the first open end of the secondary tube are influid connection with the vessel through a single opening in the vessel.The first and/or second open ends of the secondary tube may have adiameter of between 5 to 25 cm. Preferably the first and/or second openends of the secondary tube have a diameter half the diameter of thetube. Preferably the open end of the tube has a cross-sectional areawhich is between 3 and 5 times the cross-sectional area of the firstand/or second open ends of the secondary tube.

Preferably the secondary tube has a central axis and ideally a centralaxis which corresponds with the central axis of the tube. Preferably thefirst end of the secondary tube is flush with or recessed relative tothe open end of the tube.

Preferably the through aperture is of circular cross-section. Preferablythe through aperture is of consistent cross-section throughout.Preferably the through aperture extends from proximate the open end ofthe tube to proximate the closed end of the tube. The through aperturemay start within 5 to 30 cm of the closest part of the closed end of thetube to it. The through aperture may extend to or within 10 cm of aplane defined by the end surface of the open end of the tube.

The secondary tube may be spaced from the tube by one or more spanningportions. The one or more spanning portions may span the gap between theoutside of the secondary tube and the inside of the tube. Preferably atleast three spanning portions are provided. Preferably the spanningportions are evenly spaced around the secondary tube. The spanningportions may be separate from one another and/or separate from the tubeand secondary tube or may be an integral part of the tube or arepreferably an integral part of the secondary tube. The spanning portionsmay be provided along part of the length of the tube and/or secondarytube. The spanning portions may be provided for between 50% and 90% ofthe length of the secondary tube. The spanning portions may have anouter surface at least a part of which has a profile configured to matchthe internal profile of at least a part of the tube. The part may have aprofile configured to match the side wall of the tube. The part may havea profile configured to match at least a part of the closed end of thetube. The spanning portions may be in the form of pillars provided onthe secondary tube.

Preferably the secondary tube is spaced from the tube at all locationsother than those of the spanning portions. Preferably the spacingdefines one or more passageways between the inside of the tube and theoutside of the secondary tube. A passageway may be defined between eachpair of spanning portions. Preferably the secondary tube is spaced fromthe tube equally in all radial directions. The spacing between the sideof the secondary tube and the side of the tube may be between 15 cm and50 cm. Preferably the second end of the secondary tube is spaced fromthe closed end of the tube in all directions. The second end of thesecondary tube may have a spacing of between 5 cm and 30 cm relative tothe closed end of the tube.

According to a third aspect of the invention we provide a method ofmoving molten metal, the method comprising

providing a pump in fluid communication with a volume of molten metal,the pump comprising a tube, the tube being open at one end to the moltenmetal and closed at the other end, one or more side walls extendingbetween the open and closed ends of the tube;

passing an electric current through a conductor wrapped around the tube,the electromagnetic field produced causing molten metal to flow into thetube at the periphery of the tube and to flow out of the tube at thecentre of the tube.

The internal profile of the tube may be configured to promote the flowinto the tube at the periphery of the tube and/or to promote the flowout of the tube at the centre of the tube, preferably at the same time.

Preferably the method includes providing a secondary tube within thetube. Preferably the secondary tube separates the flow into and flow outof the tube and/or assists in the promotion of the stated flow.Preferably the molten metal flows into the tube along one or more spacesdefined between the inside of the tube and outside of the inner tube.Preferably the molten metal flows out of the tube through the secondarytube. Preferably the molten metal flows in a first direction into thetube and out of the tube in a second direction. Preferably the firstdirection and second direction are the opposite of one another.Preferably the molten metal under goes a change in direction at or nearthe closed end of the tube. Preferably the change in direction is causedby the closed end of the tube. Preferably the closed end of the tube isconfigured to promote the change of direction.

Preferably the flow velocity within the secondary tube is higher thanthe flow velocity in the passageway between the tube and secondary tube.

Preferably the method includes introducing the flow from the secondarytube into a vessel to which the pump is attached, preferably the samevessel as the metal is received from. The flow may be used to promotecirculation within the vessel and/or evening out of temperature and/orevening out of composition within the vessel.

Various embodiments of the invention will now described, by way ofexample only, and with reference to the accompanying drawings in which:—

FIG. 1 illustrates a prior art pumping system for circulating metalwithin a furnace;

FIG. 2 illustrates in cross-section an embodiment of a pump according tothe present invention;

FIG. 3 illustrates an end view of the pump of FIG. 2;

FIG. 4 shows the velocity profile across a conduit through whichmaterial is being electromagnetically pumped; and

FIG. 5 illustrates a pumping system for circulating metal within afurnace incorporating the pump of FIG. 2.

In a variety of circumstances it is desirable to cause flow of metalwithin a furnace or the like. The flow, for instance, improves thetemperature and chemical homogeneity of the metal.

In prior art systems, the flow is usually generated by the type ofconfiguration illustrated in FIG. 1 in plan view. The furnace 1 containsa volume of molten metal 3. An aperture 5 is provided through therefractory 7 lining the wall 9 of the furnace 1. The aperture 5 leads toa conduit 11 which is also lined with refractory 13. A flange 15 on thefurnace wall 9 opposes a flange 17 on the conduit 11 and allows the twoto be connected. A flange 19 at the other end of the conduit 11 issimilarly connected to a flange 21 on the pump 23. On the other side ofthe pump 23, a further flange 25 is used to connect the pump 23 to theoutlet conduit 27 via its flange 29. Finally the flange 31 on the otherend of the conduit 27 connects to flange 33 on the wall 9 of the furnace1 to complete the circuit. To cause flow in the furnace 1, metal ispumped out of the pump 23 into conduit 27 and hence into the furnace 1,whilst metal flows from the furnace 1 via the conduit 11 to replace it.The speed of circulation through the pumping system causes flow andhence disturbance within the furnace 1.

A significant problem with such a system is the amount of floor space itoccupies due to the need for different inlet and outlet connections andthe respective limitations imposed by the inlet and outlets from thepump. Another significant problem arises with the number of connectionswhich must be provided and maintained between the junctions of thevarious components.

In FIG. 2, an embodiment of a pump according to the present invention isprovided. This pump 100 includes within it a refractory tube 102, forinstance of silicon carbide, with an open end 104 and closed end 106.The tube 102 has a circular cross-section along most of its length so asto define a cylindrical portion 108. Towards the closed end 106 the sidewall 110 curves inwards so as to form a dome like structure for the end106.

Within the refractory tube 102 is a secondary refractory tube 112,potentially of silicon carbide. The secondary refractory tube 112 isalso open at the end 114 at which the tube 102 is open, as well as beingopen at the end 116 at which the tube 102 is closed. The open end 114 ofthe secondary refractory tube 112 ends at the same plane 118 as the end104 of the tube 102. The other open end 116 of the secondary tuberefractory 112 is spaced from the end 106 of the tube 102 so as todefine a space 120. The position of the secondary tube 112 within thetube 102 is maintained by three radial pillars 122 a, 122 b, 122 c whichextend outward from the tube 112. The radial extent of the pillars 122a, b, c is such that they contact the wall 110 of the tube 102. Thesurfaces 124 of the pillars which define their radial extent are curvedso as to match the curvature of the side wall 110 of the tube 102. Thepart 126 of these surfaces 124 nearest the end 116 of the secondary tube112 curves inward so as to match the start of the domed end 106 of thetube 102.

With the secondary tube 112 positioned within the tube 102, andreferring to FIG. 3, three passageways 128 between the tube 102,secondary tube 112 and a pair of the three pillars, 122 a, 122 b; 122 b,122 c; 122 c, 122 a are defined. These extend continuously from outside134 the pump 100 to the space 120 between the ends 106 and 116 of thetube 102 and secondary tube 112 respectively. The through aperture 130within the secondary tube 112 extends from space 120 to the outside 128of the pump 100.

Around the refractory tube 102 a single wound coil 132 is provided. Thisis clamped in position relative to the tube 102 by a framework. The coil132 forms the electromagnetic pump which is used to move the moltenmetal.

To date, electromagnetic pumps, as with other pumps, have been used totransport material along an inlet conduit on one side of the pump,through the pump conduit around which the coil is wound and then along aseparate outlet conduit on the other side of the pump. Pumpingsubstantially along an axis therefore occurs.

Within a conduit, FIG. 4, the molten metal has a velocity profile whichvaries across the width of the conduit due to the force applied to it bythe electromagnetic pump. Towards the edge of the conduit the velocityis at its highest, decreases towards the centre and is at its lowest atthe centre. The profile is generally symmetrical.

This difference in velocity profile with position is harnessed in thepresent invention. By defining the outer passageways 128 and innerthrough aperture 130 in the correct proportion the average force appliedby the electromagnetic field to the metal in the outer passageways 128is significantly greater than the average force applied by theelectromagnetic field in the through aperture 130. The net effect ofthese forces is that the metal flows from the outside 134 into thepassageways 128 into the space 120 and back to the outside 134 alongthrough aperture 130. The force on the metal in the outer passageways128 is converted by the shape of the domed end 106 into a force in theopposing direction and this swamps the more limited electromagneticforce on the metal in the through aperture 130 and causes the flow ofmaterial in the described direction. The provision of the secondary tube112 helps in establishing and maintaining this flow pattern, but someflow of this type may occurs even without such a tube, particularly onceinitiated.

By using a further reduced width of through aperture compared with thatneeded to achieve the desired flow direction, the metal can even becaused to flow down the outside at low speed, but flow through thethrough aperture at much higher speed because of the reduced unit areathe metal must flow through.

An implementation of this pump system into a furnace is shown in FIG. 5.In this case, the pump system 500 is fitted to a side wall 502 of afurnace 504. The side wall 502 is lined with a refractory 506. Thefitting is achieved using a single flange 508 on the wall 502 and singleflange 510 on the pump system 500. No other connections are needed andas a consequence a simple system is achieved. Because the inlet andoutlet conduits of the pump system 500 are provided entirely within theprofile of the pump system 500 the floor space occupied is very low.

In operation, metal 512 in the furnace 504 is drawn into the outsidepassageways 514 passes down them, into space 516 and through theaperture 518 back to the furnace 504. The relative cross-sectional areasof the inlet and outlet passages are such that a high speed jet 520 ofmolten metal is sent back to the furnace 504. This causes significantflow, disturbance and hence desirable operation across a large part ofthe furnace 504. The pump system is particularly suited for use onholding furnaces and the like.

Because of its simple design and need for only a single connectionthrough the furnace wall to the molten metal, the pump system is easy toinstall on new equipment and to retro-fit to existing situations. Thelow floor plan occupied also makes it easy to incorporate aroundexisting equipment.

1. A pump for molten metal, the pump comprising a tube, the tube beingopen at one end and closed at the other end, one or more side wallsextending between the open and closed ends, an electrical conductorbeing wrapped around the tube, a secondary tube being provided withinthe tube, the secondary tube having a through aperture extending from afirst end to a second end and being spaced from at least a part of theside wall of the tube and at least a part of the closed end of the tube.2. A pump for molten metal, the pump comprising a tube, the tube beingopen at one end and closed at the other end, one or more side wallsextending between the open and closed ends, an electrical conductorbeing wrapped around the tube.
 3. A pump according to claim 2 in whichthe internal profile of the tube is configured to promote flow into thetube at the periphery of the tube and/or to promote flow out of the tubeat the centre of the tube, preferably at the same time.
 4. A pumpaccording to claim 2 in which a secondary tube is provided within thetube, the secondary tube has a through aperture extending from a firstend to a second end and the secondary tube is spaced from at least apart of the side wall of the tube and at least a part of the closed endof the tube.
 5. A pump according to claim 2 in which the tube is ofconstant cross-section between the open end and the start of the closedend.
 6. A pump according to claim 2 in which the closed end of the tubeis formed by a tapering of the side walls and/or cross-sectional shapeof the tube.
 7. A pump according to claim 2 in which the closed end ofthe tube is dome shaped.
 8. A pump according to claim 2 in which theclosed end of the tube is initially dome inwards and has a middleportion which extends back towards the open end of the tube.
 9. A pumpaccording to claim 2 in which the secondary tube extends along the sameaxis as the tube.
 10. A pump according to claim 2 in which the secondarytube is of constant cross-section between its open ends.
 11. A pumpaccording to claim 2 in which both the open end of the tube and thefirst open end of the secondary tube are in fluid connection with thevessel through a single opening in the vessel.
 12. A pump according toclaim 2 in which the open end of the tube has a cross-sectional areawhich is between 3 and 5 times the cross-sectional area of the firstand/or second open ends of the secondary tube.
 13. A pump according toclaim 2 in which the through aperture of the secondary tube is ofconsistent cross-section throughout.
 14. A pump according to claim 2 inwhich the secondary tube is spaced from the tube by one or more spanningportions between the outside of the secondary tube and the inside of thetube.
 15. A pump according to claim 14 in which the spanning portionshave an outer surface at least a part of which has a profile configuredto match the internal profile of at least a part of the tube. The partmay have a profile configured to match the side wall of the tube.
 16. Apump according to claim 14 in which the spanning portions are in theform of pillars provided on the secondary tube.
 17. A pump according toclaim 2 in which the spacing defines one or more passageways between theinside of the tube and the outside of the secondary tube.
 18. A pumpaccording to claim 2 in which the secondary tube is spaced from the tubeequally in all radial directions.
 19. A pump according to claim 2 inwhich the second end of the secondary tube has a spacing of between 5 cmand 30 cm relative to the closed end of the tube.
 20. A method of movingmolten metal, the method comprising: providing a pump in fluidcommunication with a volume of molten metal, the pump comprising a tube,the tube being open at one end to the molten metal and closed at theother end, one or more side walls extending between the open and closedends of the tube; passing an electric current through a conductorwrapped around the tube, the electromagnetic field produced causingmolten metal to flow into the tube at the periphery of the tube and toflow out of the tube at the centre of the tube.
 21. A method accordingto claim 20 in which the internal profile of the tube is configured topromote the flow into the tube at the periphery of the tube and/or topromote the flow out of the tube at the centre of the tube.
 22. A methodaccording to claim 20 in which the method includes providing a secondarytube within the tube, the secondary tube separates the flow into andflow out of the tube and/or assists in the promotion of the stated flow.23. A method according to claim 20 in which the molten metal flows intothe tube along one or more spaces defined between the inside of the tubeand outside of the inner tube and/or the molten metal flows out of thetube through the secondary tube.
 24. A method according to claim 20 inwhich the molten metal under goes a change in direction at or near theclosed end of the tube.
 25. A method according to claim 20 in which theflow velocity within the secondary tube is higher than the flow velocityin the passageway between the tube and secondary tube.